Preheating glass batch material by melting the batch core area

ABSTRACT

Glassmaking batch material is heated to form a coherent body by heating the material progressively from a central core area, utilizing the heat insulation characteristics of the surrounding batch material to ensure the progressive melting of the batch material from the inside. Heating is preferably effected by electrodes located in a compatible molten glass core filling. A continuous process is described in which the batch material is advanced along a conveyor during treatment before passing into a glass furnace tank.

United States Patent 151 3,637,365 Oulton [4 1 Jan. 25, 1972 [54]PREHEATING GLASS BATCH [56] References Cited MATERIAL BY MELTING THEBATCH UMTED STATES PATENTS CORE AREA 2,71 l,435 6/1955 HumphreyInventor: Richard J Oulton, g l. England 3,201,219 8/1965 Ftazieret al...65/335 x 3 ilk B th i I, [7 Asslgnee P lngton r0 ers L mlted LiverpooPrimary Examiner s' Leon Bashore England ASSISIGIII Exammer-Saul R.Friedman [22] Filed: Dec. 12, 1968 Attorney-Morrison, Kennedy & Campbell[2]] Appl. No.: 783,356 [57] ABSTRACT Glassmaking batch material isheated to form a coherent body [30] Foreign Application Priomy Dam byheating the material progressively from a central core area, Dec. 19,1967 Great Britain ..57,500/67 utilizing the heat insulationcharacteristics of the surrounding batch material to ensure theprogressive melting of the batch [52] US. Cl ..65/l34, 65/335 materialfrom the inside. Heating is preferably effected by [51] Int. Cl. ..C03b3/00 electrodes located in a compatible molten glass core filling. A[58] Field of Search ..65/134, 135, 136, 335, 346, continuous process isdescribed in which the batch material is 65/347; 13/6 advanced along aconveyor during treatment before passing into a glass furnace tank.

23 Claims, 14 Drawing Figures PATENTEDJANZSIBYZ 3.637.365

sum-so; e

lorne y PREI-IEATING GLASS BATCH MATERIAL BY MELTING TI-IE BATCH COREAREA BACKGROUND OF THE INVENTION This invention relates to methods ofheating glassmaking batch material and to apparatus therefor.

In the art of melting a glassmaking batch material in a tank furnace,the batch is customarily fed onto the molten glass in a tank at the coldend thereof so as to form a blanket of the material on the molten glass.The blanket is heated by products of combustion injected into theheadspace of the tank furnace across the blanket, alternately from oneside and then from the other of the tank at the usual regular intervals.

As the blanket moves along the tank towards the hot end, theundersurfaee of the blanket is heated by the molten glass and the uppersurface is heated by the products of combustion projected across thetank. The products of combustion which heat the upper surface of theblanket are at a much higher temperature than that of the molten glassbeneath the blanket, and it is not until the blanket is sufiicientlythin that the ancillary heat of the molten glass produces a uniformconcomitant heat treatment on both surfaces of the layer constituted bythe thinned blanket and it is not until the batch material is in thisthin layer form that uniform heating occurs.

A main object of the present invention is to achieve an economic methodof continually and uniformly heat treating glass batch forming material,and a further main object is to attain uniform heating of the batchmaterial to the stage of converting the batch material into a moltenstate.

SUMMARY In heating glass forming batch material according to the presentinvention a novel principle of operation is involved in which the heatsource for heat treating a batch material is enveloped by a surroundingbody of the batch material so that the surrounding body of glass formingbatch material is utilized as a heat insulation about the heat source toensure that all the emitted heat is efficiently employed in effectingthe desired uniform heat treatment of the surrounding batch material.

From another aspect the underlying principle may be visualized as one inwhich the required heat source is created in a core area of a body ofthe glass making batch material to be treated.

Accordingly, a method of heating glassmaking batch material according tothe invention is characterized by forming a coherent body of the batchmaterial and effecting the desired heat treatment by creating a heatsource in a core area of the coherent body while retaining the heatinsulating characteristics of the surrounding batch material to ensureoptimum use of heat developed in the core area to melt the surroundingbatch material progressively.

Accordingly at all times the surrounding batch material functions toinhibit heat losses from the core area.

In accordance with the invention a coherent body of granu lar batchmaterial may be formed into desired shape on a support or by filling thebatch material into a suitable shaped container. The granular materialutilized in either circumstance may be batch material which has beengiven a sufficient quantity of moisture (up to percent content) toengender cohesion throughout the body during the heating operation.

A heating process carried out in accordance with the present inventionmay consist of a process of preheatingbatch material as a step precedentto feeding the batch material to a tank furnace, thus the heat treatmentmay extend to melting the lower melting point components of the batchmaterial so as to form a matrix about the components of the highermelting point, or the components of the batch may be arranged in layerform, the layers being graduated according to the melting points of thecomponents in each layer, e.g., as hereinafter more particularlydescribed.

However, an especial heating process according to the "uh vention may bea heat treatment which results in-at least the major volume of thecoherent body being converted into a molten body of glass compatiblewith a molten glass held in a glass melting tank to replenish the tankas fined molten glass is withdrawn therefrom.

Accordingly the heat source employed in a method of operation accordingto the invention may be provided by creating in the core area a heatsource consisting of molten glass and automatically increasing thevolume of molten glass by the addition of freshly melted batch to theheat source as the internal batch surface defining the core arearetreats and the volume of the core area increases.

Having created a heat source of molten glass in the core area,continuous heating may be achieved in accordance with the invention byutilizing the conductivity of the molten glass to engender sufficientheat to progressively melt the retreating batch face. This method ofconverting the batch material into molten form ensures a continuousagitation of the molten glass engendered by convection currents and bythe agitation a homogeneous glass is maintained in the heat source.

In operation, the heat source in the core area immediately operates onthe adjacent surface of the surrounding body of glassmaking batchmaterial and the original volume of molten glass will be increased bythe continual flow of molten glass derived from heat conducted fromtheheat source to the innermost surface of the surrounding batchmaterial, in other words the thickness of the surrounding batch materialmeasured radially from the core area will correspondingly increase asheating continues and the inner face immediately surrounding the corearea is continually being melted and renewed, and in consequence theinner face of the surrounding material is continually retreating fromthe heat source occupying the core area.

The coherent body of batch material may be encased in a retaining wallto maintain sufficient structural strength in the body when the internalbatch surface defined in the core area has retreated to outer regions ofthe coherent body.

Alternatively, the retaining wall may be formed by fritting the outerregion of the formed coherent body.

The retaining wall may be formed of wood, in which case the heatingprocess would be stopped when the lining of the surrounding body ofbatch material has obtained a thinness such that heat is transmittedthrough the wall at a rate to burn the containing wall. When significantamounts of heat reach the retaining wall of wood the heating operationis arrested, so that the accumulations of molten glass in the fringecore area may be discharged, and the wooden wall, lined with hot hatchmaterial, recharged for a further heating operation.

The present invention accordingly provides economically efficient means,i.e., from the point of view of use of heat emitted from the heatsource, of producing relatively small quantities of different types ofglasses, varying in color hues, or varying in characteristics, such asof refraction, or of coefficient of expansion or contraction.

Alternatively, when the molten glass produced is to constitute a meansof supply of molten glass to a glass melting tank (or a pot), e.g., inregard to a melting tank, in a volume in compensation for the volume offined molten glass withdrawn from the tank, the retaining wall is formedof a glass compatible with the molten glass formed from the batchmaterial and then if the heat transmission to the wall is such that thewall collapses, the softened wall and lining of unmelted batch materialmay be discharged with the molten glass into the melting tank.

Instead of surrounding the heat source with a conventional homogeneousbatch material the heat source may be surrounded by a coherent body ofbatch material in layer form, constituted in such a way that the layercontiguous to and surrounding the core area comprises one or more of thebatch components having the highest melting point, the succeedingsurrounding layers comprising components of progressively lower meltingpoints.

Where the heat source in the core' area is constituted by molten glass,the heat source may be formed by charging into the core area compatiblecullet and the cullet melted to expedite the creation of a heat sourceof an electrically conducting body of molten glass in the core area.

To this end there may be provided in the core area constructed accordingto the invention a coiled compatible glass in proximity to the innennostbatch surface defining the pristine core area with which glass isoperatively associated an electrical conductor to expedite the creationof an electrically conductive heat source of molten glass in the corearea of the coherent body of batch material. Preferably, andparticularly where the batch material comprises a water content for thepurpose of engendering cohesion throughout the body during the heatingoperation there may be formed above the heat source a concentric tubulargas vent constituted by a track of loosely packed batch materialextending from the central part of the pristine core area to the surfaceof the coherent body at the level of the top of the retaining wall,whether the wall be wood or of glass.

By locating the higher melting point components of a glassmaking batchmaterial about the core area higher starting temperatures may beutilized hence a correspondingly high energy input is possible instarting up, at which time the maximum heat insulating from the batchmaterial is available.

From the foregoing it will be appreciated that the present inventioncomprehends the construction of a portable coherent body of glassmakingbatch material having a vacant core area constituted by a central socketof small volume as compared with the volume of the coherent body, saidsocket being adapted for the reception of a heat source for continuallytransmitting heat to the coherent body whether the heat source isinitially a molten body or is converted into a molten state during theinitial phases of a heating operation.

The present invention further comprises a method of feeding glassmakingbatch material to a glass melting tank furnace characterized by locatingin the doghouse of the furnace in coaxial alignment with a set ofburners mounted in ports in opposed walls of the doghouse a tubular bodyof coherent batch material, so that a flame at batch melting temperatureis alternately projected into the bore of the tubular body of the batchfrom each end thereof and simultaneously fritting the outer surface ofthe tubular body by utilizing the ambient heat in the doghouse duringthe progress of melting the batch in the core area continually definedby the progressive retreating inner surface of the batch as meltingtakes place and then rolling the heat treated batch into the moltenglass in the furnace tank.

The invention also comprises a method of feeding glassmaking batchmaterial to a glass melting tank furnace characterized by making (e.g.,by extrusion or pressing) a rollable hollow body of the batch, applyingsufficient heat to the batch through the bore of the hollow body toprogressively melt the material defining the bore maintaining theinternal heat treatment so long as the wall thickness of the body issufficient to ensure rollability, advancing the internally melted bodyinto the feeding end of the tank and allowing it to dwell in the feedingend thereby subjecting the external surface of the hollow body to theheating effect of the furnace gases and thereafter rolling the heatedbatch into the molten glass in the tank.

Further the present invention comprises a modified method of heatingglassmaking batch material which method is characterized in that theheat source in the core area of the batch material is formed byspreading a thick layer of coherent batch material on a defonnablesupport channelling the layer and pouring molten glass into the centralarea of the channel, covering the molten glass with a thick layer of thebatch material, projecting aligned electrodes in spaced relation intothe molten glass and energizing the electrodes.

The present invention also comprises apparatus devised for heating ormelting batch material according to the method of operation inaccordance with the present invention said apparatus being particularlydescribed and defined in the accompanying apparatus claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectionalelevation of one form of electrical heating apparatus taken on the lineIl of FIG. 2, and

FIG. 2 is a plan of the apparatus shown in FIG. I.

FIG. 3 is a vertical sectional elevation of a modified form ofelectrical heating apparatus taken on the line IIIIII of FIG. 4, and

FIG. 4 is a plan of the apparatus shown in FIG. 3,

FIG. 5 is a pictorial view of the electrode support included in theapparatus shown in FIGS. 3 and 4;

FIG. 6 shows in vertical sectional elevation a further modified form ofheating apparatus according to the inventron,

electrical heating apparatus in which the batch material is assembledfor heating in concentric layer form, and

FIG. 8 is a detail view, in sectional elevation, of the apparatus shownin FIG. 7,

FIG. 9 is also a detail view, similar to FIG. 8, showing a modifiedelectrical heater for starting up the conversion of the batch materialinto a molten state,

FIG. 10 is a series of plan diagrams showing a layout for stage by stageheating of glassmaking batch material, intended for producing from agroup of coherent bodies of the batch material, molten glass for supplyto a glass melting tank furnace in compensation for fined glass takenfrom the tank,

FIGS. 11 and 12 illustrate an alternative method of melting wherein thebatch material is of tubular form and heating is effected by projectinghot gases into each end of the bore alternately and allowing dischargeat the other end. FIG. II is a sectional plan view of the doghouse of aglass melting furnace and FIG. 12 is a section on line XII-XII withburners within and outside of the doghouse, and

FIGS. 13 and 14 show in sectional elevation and side elevationrespectively a method of operation according to the invention whereinthe coherent glassmaking batch material is wrapped around a heater toform a core arm occupied by the heater and a confining wall envelopingthe heater, as hereinafter more fully described.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the apparatus illustrated inFIGS. 1 and 2 a containing wall constituted by wooden barrel 11 has abottom 12 and top 13. An electrode 14 passes through an opening 15 inbottom 12 and an electrode 16 passes through an opening 17 in top 13,the electrodes 14 and 16 extending axially of the barrel and terminatingshort of the midlength thereof so that the inner ends of these coaxialelectrodes 14 and 16 are in spaced relation.

A glass tube 18 formed of glass compatible with the melted constituentsof the batch material in the barrel extends from the top 13 axiallydownwards past the midlength of the barrel to terminate below the upperend of the electrode 14 and a filling 19 of loose batch material fillsthe upper regions of tube I8 in the nature of a porous plug therein andhas an axial bore 20 to allow passage of electrode 16 therethrough.

A volume of molten glass 21 is poured into the lower regions of tube 18to surround the upper end of electrode 14 and the upper level of themolten glass 21 lies above the level of the lower end of electrode 16.Thus, the inner ends of both the electrodes 14 and 16 are surrounded bythe molten glass 21 and the molten glass 21 thereby constitutes part ofa conductive path for an electric heating current passing between theelectrodes 14 and 16. The whole of the barrel 1], externally of tube 18,is filled with batch 22 so that electrode 14 and tube 18 are envelopedby the batch 22 to be treated.

To erect the heating assembly, electrode 14 is passed through theopening 15 in bottom 12 and secured in the barrel in position by anexternal insulated conducting plate 23 which has an electricalconnector, as indicated at 24, for connection to a suitable electricalmains. The barrel is then partially filled FIG. 7 is a verticalsectional elevation of another form of with batch material 22 to a leveljust below the upper end of electrode 14, the tube 18 is positioned inthe barrel with the exposed inner end of electrode 14 located coaxiallywithin the lower end of tube 18 and the filling of the barrel with batch22 is completed. A molten glass 21 is then poured into the glass tube18, a batch filling 19 is located into the tube 18, the top 13 ispositioned to close the upper opening end of barrel l1 and electrode 16is passed through the opening 17 in lid 13 and through a bore 20 formedin the porous filling 19 until the inner end of electrode 16 contactsand is immersed in the molten glass 21. It will be observed that thediameter of each electrode is, in the embodiment shown, considerablyless than the diameter of the body of molten glass 21 within the tube18, the purpose of which is to maintain thermal agitation as hereinafterfully explained.

The porous filling 19 in the upper part of the tube 18 is a filling ofloose batch material which filling provides in its interstices tortuouspassages for the escape of gases generated during the chemical reactionswhich take place during the melting of the batch material as well knownin the art and of water vapor derived from the water content of thebatch material within the container wall.

By separating the gases of reaction from the molten glass before themolten glass is introduced into a glass melting tank of normal form theamount of gases released in the tank are significantly reduced and thenormal experience of dilution of the tank atmosphere correspondinglyrestricted. Further, the molten glass fed to the tank has a temperatureexceeding the melting temperature of the glass, and apart from achievingmaximum extraction of the reaction gases, a greater heat contribution tothe molten glass in the tank occurs. Since the molten glass producedaccording to the invention has already released a proportion of thegases in solution a further reduction in the volume of the gases to bereleased during the travel of the glass through the tank is experienced.

It will be seen from the above arrangement that the core of molten glass21 constitutes a heat source which can only lose heat through the wallsof tube 18 to the enveloping batch 22. The lower regions of tube 18 aresoon melted by the molten glass 21 and become absorbed into the ambientmolten body of glass 21 so that at this stage the heat sourceconstituted by the molten glass 21, is intimately surrounded by batch22, the core of molten glass 21 therefore can only lose heat to thesurrounding batch 22 and the only heat loss from the system in theinitial stages will be heat conducted along electrodes 14 and 16 so thata very high heat transfer efficiency to the batch is obtained.

The surrounding batch 22 will have a temperature at about thetemperature of the contiguous molten glass 21, but, because the batch 22is a good heat insulating material, a severe temperature gradient willbe established through the batch 22 immediately adjacent the core ofmolten glass 21 and the outer regions of the batch 22 effectivelyinsulate the timber parts of the barrel 11 from the heat source 21 sothat the barrel 11 will not be subjected to detrimental heating untilthe major part of the batch 22 is at a temperature above 800 C The heatsource 21 is maintained at the desired temperature, i.e., above 1,000C., by passing an electric heating current between electrodes 14 and 16.This causes that part of the molten glass 21 lying directly betweenelectrodes 14 and 16 to be heated to a temperature above the averagetemperature of the body of molten glass 21, thereby creating a column ofhigh temperature glass within the body of glass 21. As hot thin glasswill always rise through a body of molten glass at lower temperature,thermal currents will be established in the body of molten glass 21 andsaid molten glass 21 will be in a constant stage of agitation.

This thermally induced agitation causes a mixing of the molten glass 21and as the batch adjacent the molten glass 21 melts it is stirred intothe body of molten glass 21 and forms an integral part thereof.

It will be appreciated that although a thermal agitation within theglass 21 will be established, the outer surface of the glass body 21will be continuously losing heat to the surrounding batch 22 so thatthere will be little movement at the outer surface of the glass body 21and very little scraping of the batch will be experienced. This means ineffect that batch 22 will only be absorbed into the glass body 21 whenthe ambient batch has attained a temperature above the "flow temperatureof the glass 21. [f the batch 22 has been uniformly mixed it will, atthe flow temperature of the molten glass 21, have been substantiallyconverted into glass form and, therefore, the presence of unmeltedparticles in the molten glass 21 will be very limited, and any suchparticles will be moved about within the glass 21 by the thermalagitation thereof, so that, the dissolving or absorption of particleswill be accelerated in the hot glass flow. In use the filling 19functions as a vent for gases in the heating zone-which gases heat thefilling as they are released from the heating zone.

The batch 22 may be compacted granular material and the batch materialmay contain a modicum of moisture to assist in maintaining a coherentmass within the barrel 11.

FIGS. 3 to 5 show an alternative heating assembly wherein the containingwall is a glass cylinder 25, open at both ends, vertically disposed on afloor constituted by a glass plate 26 supported on horizontal bars 27and 28 by which the assembly can be conveyed from place to place. Batch22 is charged into the glass cylinder containing wall 25 and iscompacted to leave a cylindrical bore 30, which bore extends axiallydownwardly past the midlength of wall 25, as indicated in FIG. 3. Aquantity of molten glass 21 is introduced into the axial bore 30 so asto fill the lower regions thereof and parallel electrodes 32 and 33,held in spaced relationship by an insulating crossmember 34, see FIG. 5,are lowered down the bore 30 until the inwardly turned feet 35 and 36 ofelectrode 32 and 33 respectively are totally immersed in the moltenglass 21.

The axial bore 30 is then filled with loose batch 19 so that the heatsource, constituted by the molten glass 21, is wholly enclosed by batchwhile gases created during the conversion of batch to glass can escapeupwardly by passing through the loose batch 19 within the axial bore 30.Said gases, in passing through the loose batch 19, are thus forced toimpart heat to the loose batch 19 so that in the initial heating stagesalmost the only heat lost from the assembly is by conduction through theelectrodes 32 and 33 to atmosphere.

With this arrangement an electrical heating current applied throughelectrodes 32 and 33 is caused to flow through the molten glass 21 lyingbetween the juxtaposed lower ends 35 and 36 of electrodes 32 and 33respectively and the heat generated in the molten glass 21 istransmitted by conduction and by convection, due to the thermalconvection currents induced in the molten glass by the heating currentand agitating the molten glass, so that the average temperature of themo]- ten glass 21 is maintained at the desired level.

Because of the heat insulating properties of the batch materials 19, 22a severe temperature gradient will be established through the batchmaterial immediately adjacent the molten glass 21 so that in the initialpart of the heating process very little heat will be transmitted to thecontainer walls constituted by the glass cylindrical wall 25 and glassplate 26. As the batch 19, 22 adjacent the molten glass 21 is melted andabsorbed into the core 21 of molten glass constituting the heat source,the amount of batch insulating the molten glass 21 from the containerparts 25, 26 is reduced and eventually heat will be transmitted to theseglass parts.

At this stage, the electrodes 32 and 33 can be removed and the entireassembly i.e., the molten glass 21, unmelted batch 22 and the glass walland bottom parts of the container can all be introduced into the meltend of a glass melting tank or into a melting unit. Alternatively, onlythe molten glass and unmelted batch may be introduced into the tank ormelting unit so that glass cylinder 25 and plate 26 can be recharged andused over again.

During the heating cycle it may be desirable for the path of theelectric heating current to be moved within the arrangement and theunitary arrangement shown in FIG. constitutes means readily affordingsuch displacement.

The insulating connecting plate 34 supporting electrodes 32 and 33 hastwo arms 43 and 44, see FIG. 5, extending therefrom and the arms 43 and44 have extendable feet 45 and 45 respectively which feet rest on theupper surface of the batch in the container wall 25. Thus the verticallocation of the electrical heating path can be varied by adjusting thefeet 45 and 46 relative to arms 43 and 44 respectively.

Although the foregoing examples show the use of only one electrical paththrough the molten glass it will be appreciated that more electrodes canbe installed either during the initial part of the heating cycle or at alater stage in the heating cycle and thus the actual electrical heatenergy imparted to the assembly can be increased or reduced as required,or if as already explained it is desired to change the path of theelectrical current, then the electrical arrangement shown in FIG. 5 canbe readily used and adjusted.

In the two described embodiments of the invention the total heatrequired to melt the batch is imparted with very high efficiency and,dependent upon the size of the container and. the volume of batch, morethan 50 percent of the total heat required for melting can be directlytransferred to the batch surrounding the heat source during the heatingprocess.

As long as the exterior of the container is not losing much heat, thethermal efficiency is very high, and therefore additional heat can beimparted to the batch with the same high rate heat transfer efficiency.

' Thus, with the assembly shown in FIGS. 3 to 5 a high heat transferefficiency is obtained up to the stage at which the glass cylindricalwall and/or plate 26 begins to release heat to its surroundings. Byintroducing the assembly into thermal surroundings which will reduce oreliminate the heat loss from the container then the heat input to thebatch can be increased without loss in efficiency.

FIG. 6 shows a further embodiment of the invention and wherein acoherent body of batch 22 has a central axial bore extending downwardlybelow the midlength of the body 22. A radiant heating element 50,supported by a removable batch cap 51 having a boss 52 closing the upperend of bore 30, imparts radiant heat to the surrounding batch 22 toeffect a heating, and eventually a conversion to glass of the batch inthe region of the batch wall defining the bore 30. It will beappreciated that with this arrangement the converted batch will flowdown the bore 30 to collect in the lower regions thereof and, after theheating process has passed a predetermined limit, electrodes for passingelectric current through the converted batch can be substituted for orused in addition to the radiant heater 50. Alternatively, radiantheaters of different shape and power rating may be used during the laterstages of heating.

The foregoing examples have been limited to the heating of conventionalbatch mixture. This is not an essential of the present invention andFIG. 7 shows one example wherein glass can be made with the constituentsinitially in separated form, so that selected constituents can bearranged to lie in concentrated layer form in specific locations of thebody.

In the embodiment illustrated in FIG. 7 a container, comprising acylindrical glass wall 25 with a glass bottom plate 26 is lined withbatch 22 and filled with selected layers of glass making constituents22a, 22b and 220 which surround the lower regions of an axial bore 30extending downwardly into the batch, past the midregion thereof.Electrodes 32 and 33, constructed as illustrated in FIGS. 3 to 5 andheld in spaced parallel relationship by an insulating plate 34, arepassed down into the blind bore and the bore is filled with loose batch19 to allow for the escape of gases.

In this case, the heating process is initiated from cold by a glass tube54 (see FIG. 8) which extends between the inwardly turned feet 35, 36 ofelectrodes 32 and 33 respectively, which tube 54 is coated withelectrically conductive material such as a colloidal graphite. Whenheating current is first passed between the electrodes 32, 33 thecurrent passes through the electrically conductive material on the glasstube 54 until the glass tube 54 is sufficiently heated as to becomeconductive, after which the tube constitutes the heat source in a corearea of the batch for transmitting heat to the surrounding materials.The tube 54 is so arranged that after it melts the molten glass forms apool which continues to be heated by current passing between theelectrodes.

The separated layer arrangement of the glassmaking constituents as shownin FIG. 7 may be carried out for a number of reasons such as to allowthe longest heating time for the most difficult constituent, i.e.,either die constituent with the highest heat insulating value, or togive a longer heated period for the reaction of two difiicultconstituents. As the heat input increases the thermal convectioncurrents in the molten glass will cause a stirring of the molten glassmaterial which is fluid within the insulating blanket of batch 22 sothat a mixing of the constituents can be carried out after heattransmission to the separated constituents. The present invention canaccordingly be utilized to arrange the reaction of the constituents in adesired sequence but care must always be taken to ensure that the heatsource is maintained electrically con ductive as and when desired in theprocess. As all the layers will be reacted before the batch lining 22 isheated to melting temperature a homogeneous glass mixture can still beobtained from the separated constituents before the container 25, 26reaches collapse temperature.

In FIG. 9 there is shown an arrangement giving a longer conducting paththan that of FIGS. 7 and 8 and therefore a higher heat input during theinitial stages.

As shown in FIG. 9, the two electrodes 32, 33 have feet 35, 36 arrangedin a manner similar to the electrode feet 35, 36 of FIGS. 3 to 5. Inthis case, however, electrode 33 has a lug 36a and this lug is connectedto the foot 35 by a spiral glass rod 54a having an electricallyconductive coating. This spiral rod 54a, when supplied with electriccurrent by the electrodes 32, 33 heats a much larger volume than thatheated by the tube 54. A volume of cullet c may be placed at the upperend of the spiral rod 54a, to assist the formation of a volume of moltenglass in the initial stages of heating. When the rod 540 is meltedcurrent flows between the feet of the electrodes 32, 33 as in the FIG. 3arrangement.

It will now be appreciated that the present invention comprehendsheating glassmaking batch materials in either conventionally mixed batchor batch in layer form as herein described by allowing heat to betransmitted to the batch from a central internal heat source so that thebatch is utilized to insulate the heat source and the high insulatingcharacteristics of the materials are used to assist the heating processrather than resist said process as is experienced with most of thepreviously known heating methods.

The proposed heating process can be instigated from a hot start i.e., byintroducing a molten body of glass into the glassmaking materialsforming the batch, or from a cold start by introducing a heating elementsuch as tube 54 in FIG. 8 which is conductive at low temperatures, asdescribed with reference to FIG. 7, 8 and 9.

FIG. 10 shows diagrammatically an installation which allows the heatinput to the batch to be increased, while retaining the high heattransfer efficiency after the container wall begins to receive heat fromthe interior of the assembly.

In the illustrated example a chamber 56, in this case of rectangularcross section, has an atmosphere at a temperature in the region of 200C., and contains eight heating components of the type illustrated eitherin FIG. 1 and FIG. 2, or in FIGS. 3 to 5, or in FIG. 6 or in FIGS. 7 and8 or 9, and indicated generally by the reference A, a second chamber 57contains three such components and has an atmosphere maintained in theregion of 550 C., and a third chamber 58, which is a high temperaturechamber, i.e., having an internal temperature above 800" C., isdimensioned to contain only one such component. The chambers 56 and 57have electrical means for maintaining the supply of energy to electrodessuch as electrodes 32 and 33. The floor of the chamber 58 is supportedby two bars, 27 and 28, and the chamber 58 is located by the barsdirectly above the molten glass in the melt end of a continuous glasstank or a melting unit (not shown).

The installation illustrated in FIG. is intended for the supply of rawmaterials to a glass melting furnace, and each heating component of theassembly in chamber 58 contains sufficient raw materials to supplymolten glass in replacement of the quantity of glass drawn off from theworking end of the furnace in 1 hour. This means that an appropriateassembly of components must pass per hour through chamber 58 and thecomponents of the heating assembly each comprise floor plate 26 andcontaining wall 25, the molten glass within the containers and the smallamount of unmelted batch remaining in the container 25, 26 must fallfrom chamber 58 into the molten glass therebeneath within an hour.

The installation shown in FIG. 10 includes 40 heating components in theinitial heating stage, said 40 components each having their heatingcycle initiated at 1 hour intervals and, because at this stage thecontainers 2 are not receiving heat from the contents thereof, said 40components can be exposed to the atmospheric air.

As the most advanced assembly of the 40 components reaches that stage inthe heating cycle where the transfer of heat from the interior heatsource becomes evident by an elevation of the temperature at thecontainer wall, such components are moved into chamber 56 where theambient temperature (200 C.) exceeds that of the containing wall 25 sothat loss of heat from the component is inhibited and the internalheating process continues with very high efficiency. Again, as thesurface temperature of a component in chamber 56 increases above thechamber temperature the component is moved out of the chamber 56 intochamber 57 which has a higher ambient temperature (550 C.) so that heatlosses from the component are arrested and the very high heat transferefficiency of the internal heating arrangement is maintained.

Each component has such dimensions and such an arrangement of heatsource that up to this stage the floor plate 26 is the coldest part ofthe component so that movement of the components, by forklift trucks orroller conveyors, is readily effected and, if necessary, cold airdraughts can be directed against the underside of the floor plate 26 tomaintain said plate in a stable condition to support the component overa roller conveyor or other conveying means.

It will be appreciated that as the heating operation progresses andbatch is converted into glass and absorbed into the heat source, thevolume of the heat source increases and the volume of the batchaffording heat insulation to the heat source decreases as the innersurface surrounding the heat source retreats.

The heat insulating walls of batch surrounding the heat source in eachcomponent thus diminish in thickness and the transfer of heat to thesurrounding casing and floor 26 is effected with increasing rapidity.Thus, while an initial heating period of 40 hours may be necessarybefore increased surface temperature of the container wall becomesevident it may only take 8 hours for the rate of heat transfer to thesurface to increase so that the surface temperature of the containerwall reaches 200 C. above the temperature of the atmosphere, and a mere3 hours before the surface temperature reaches 550 C.

When the surface temperature of a component in chamber 57 exceeds thetemperature in chamber 57, i.e., 550 C., the electrodes 32 and 33 areremoved from the component and the component is moved into .chamber 58where it is supported on rails 59 and 60. The chamber 58 is open betweenthe rails 59, 60 to the atmosphere over the glass tank and is therebyvery hot i.e., 800 C., and each floor plate 26 is also exposed to heatradiation from the glass tank and the atmosphere above.

Further, the component now contains a very large volume of molten glassand only thin walls of batch insulating the molten glass 21 from theenclosing walls 25 and floor plate 26 so that these parts of thecomponent are rapidly heated and in less than 1 hour attain atemperature at which the glass, of which they are composed, is no longerrigid enough to retain its contents so that the component collapses andfalls with contents into the molten glass therebelow.

It will be appreciated that throughout the heating cycle the externalsurfaces of each assembly of components will always be the coldest partthereof so that at the collapse point the contents of each componentmust be at a temperature above the collapse temperature of thecontaining wall such as 11 or 25, and the actual heat input required tobe supplied to the unmelted batch by the furnace will be only a verysmall part of the total heat required to raise the component and itscontents to melting temperature.

It will be appreciated that the numbers of components in each specificchamber and the number of chambers and the temperatures of theatmosphere in these chambers have been recited only by way of exampleand the actual heating cycle for each assembly will depend on the volumeand shape of the assembly, the volume of molten glass in the heat source21 initially introduced into the arrangement and the strength andduration of the electric heating current.

During the initial part of the heating process large quantities of heatcan be imparted to the glassmaking materials, with negligible heatlosses from the system and with very little capital expense on housingthe components of the assemblies for heating. Further, by providingchambers to house components having atmospheres heated to only lowtemperatures relative to the avei'age temperatures through the heatingarrangements the heat input to the glassmaking materials can beincreased for very little additional capital cost.

The process according to the invention can be continued untilpractically the whole of the volume of each heated component has beenconverted to glass and the discharge of the molten glass and heatedmaterials into the next heating stage is effected without introducingundesired matter into the glass.

The delivery of preheated glassmaking materials and molten glass to atank furnace by the method according to the present invention not onlyprovides a very efficient and cheap method of heating the glassmakingconstituents but also reduces the melt area required in the tank so thatthe output of a given tank size is substantially increased.

It will also be appreciated that the present invention is dependent uponthe establishment of a steep temperature gradient between the exteriorof a body of glassmaking materials and a heat source within the body.The heat source is preferably maintained at an average temperature above1,000 C. and the thickness of the materials surrounding the heat sourceis preferably such as to allow the establishment and maintenance of avery severe temperature gradient in the glassmaking materialsimmediately adjacent the heat source.

The addition of heating apparatus into the heat source can beprearranged by, for example, symmetrically burying about the core areaadditional electrodes in the body of glassmaking materials so that thematerials in the region of each electrode are sufficiently heated tobecome electrically conductive, and become ancillary means of heatingthe core area.

In one method of feeding preheated and/or melted batch material to aglass melting furnace the batch, made in coherent tubular form andinternally heated, is rolled along the floor of the doghouse on tomolten glass in the tank of the furnace when the heating operation iscomplete. The body may be internally heated by directing a melting flameinto its bore.

In one method of supplying molten batch material to the tank of a glassmelting furnace according to this aspect of the present invention, thebatch, made in coherent tubular form, is located in the doghouse incoaxial alignment with a set of burners mounted in opposite walls of thedoghouse so that a flame at batch melting temperature is alternatelyprojected into the bore of the tubular body of batch from each endthereof and simultaneously the outer surface of the tubular body issubjected to the ambient heat in the doghouse by which the outer surfaceis fritted and thereby reinforced sufficiently to be rolled along thefloor of the doghouse from the burners to the molten glass in the tank,to which tank is fed the heated shell of batch material as well as themolten glass.

In an alternative method of feeding glassmaking batch material to thetank of a glass melting furnace according to the present invention, thebatch formed into a rollable coherent tube (e.g., by extrusion orpressing) is deposited on a support outside the doghouse and there isinternally heated by a first set of burners.

The heat is preferably derived from either gas or oil burners, whichburners project a flame at a batch melting temperature into andcoaxially with the bore of the tube to progressively melt, in an outwarddirection, the interior batch surface which surface continually definesthe core area of the tubular batch body during this melting stage.

This heating operation may be the first stage of a heat treatment of thebatch according to this aspect of the invention and the second stage iseffected in the doghouse where the enlarged bore of the tubular body ismade available to the coaxial burners in the doghouse.

In the second stage the heating may continue until the wall thickness ofthe tubular body of the batch is approaching, but has not achieved, thethickness dimension at which the wall has insufficient strength tomaintain its tubular form as it rolls away from the doghouse burners onto the molten glass in the tank.

After the internal batch heating operation has been completed to thedesired extent whether or not it has been carried on to the extent ofapproaching the minimum wall thickness for maintaining the tubular formof the batch, it is pushed by rods or the like passing through thedoghouse door to initiate the rolling movement desired to move the batchfrom the bumersto the molten metal.

To facilitate the rolling, the floor of the doghouse may be inclineddownwardly from the location at which the tubular batch dwells inregister with the burners to the molten glass in the furnace tank andmay terminate below the surface of mo]- ten glass in the tank. Heatersmay be embedded near the forward edge of the floor.

Apparatus in accordance with this aspect of the invention for use incarrying out the heat treatment of glass forming batch material in aglass melting tank furnace is characterized by coaxial burners mountedin opposite ports in the sidewalls of the doghouse at a height above thefloor of the doghouse equal to half the diameter of a tubular body ofcoherent batch material.

Reference has hereinbefore been made to a set of burners, either in thedoghouse only or in the doghouse and outside the doghouse, and thereference-is meant to include aligned flame projecting means, eachwithin a port, which port acts as an exhaust port for the oppositeburner and vice versa when the burners are changed over as occurs withburners in ports formed along the tank wall of the furnace structure byassociating the ports and burners with a reverberatory furnace heatingsystem.

Such a method of feeding glassmaking batch material to a glass meltingtank is diagrammatically illustrated in FIGS. 1!

v and 12 of the accompanying drawings.

In the illustrated arrangement the batch is formed by extrusion into atube 22. A gas or oil burner flame is directed from a port 62 throughthe bore of the tube and is exhausted through an exhaust port 63. Thetube of batch 22 thereby serves to contain the flame and in consequencethe batch 22 is heated from an internal heat source and in the core areaof the tube.

The heating arrangement illustrated works on a two stage basis. In thefirst stage, the burner set 62, 63 heats a tube 22 of coherent batchmaterial outside a glass melting tank and after the heating hasprogressed to a predetermined stage, the tube of batch 22 is advancedinwardly by a pusher 64 so as to roll it from a supporting conveyor 65through a doorway normally closed by a door 66 on to the floor 67 of thedoghouse 68 of a glass melting furnace to a second heating stageposition where the tube 22 is aligned with a second burner and exhaustset 69. for completion of the internal (or core area) heating operatron.

During the second heating stage the tube 22 is submitted to the heat inthe doghouse 68 which heat is sufficient to frit the external surfaceand thereby reinforce the batch wall to permit the final rolling of thebatch to the tank of molten glass in the furnace when the internalheating is completed.

By converting batch material into a molten state according to theinvention a very rapid heat transfer can be carried out by this methodand by making the direction of the flame reversible between the ports62, 63 and ports 69, 70 e.g., by using a reverberatory furnace inassociation with the said ports approximately uniform melting isobtained and a good heat exchange efficiency between the flame and theinternal wall of the tube 22 is achieved.

When the tube 22 has been subjected to the flame between ports 69 and 70for the desired period the tube 22 is moved along the doghouse floor 67on to the molten glass in the tank. The batch melting operation isallowed to continue with the heat travelling outwardly from the corearea of batch material into the progressively thinning containing wallof the batch, and the heat of the molten glass in the melting tank andthe heat in the tank atmosphere simultaneously apply internal andexternal heat to the floating tube 22 to complete a very rapid andeconomic melting cycle, as compared with that achieved in a normal glassmelting tank operation where the glass forming batch material is fed tothe tank in granular form and covers the molten glass like a blanket onthe molten glass.

The tubular body of coherent batch 22 may be a unitary body of thedesired length or may be made up of a plurality of short lengths inend-to-end abutment.

Instead of preforming a coherent body of glassmaking batch material witha defined core area as hereinbefore described the body shape and corearea may be continually produced about a heating source constituted bymolten glass at the same time as the heat source, wholly insulated bythe batch material, is activated by energized electrodes to utilize themolten glass as an internal conductor of heat at melting temperature tomelt the batch material where it embraces the molten glass.

To this end and in accordance with the invention, there is deposited ona base constituted by a thick layer of batch material, a medial bed ofmolten glass, and the molten glass is covered by another thick layer ofbatch, the base layer being deformed upwardly from the margins to form achannel sloping from each side towards the middle to locate the heatsource constituted by the molten glass, and over the channel electrodesare suspended and precisely lowered in to the covered bed of moltenglass and energized to utilize the molten glass as an internal heatsource insulated by the batch material.

According to this invention there are two concomitant steps, viz,encapsulating a core of molten glass with a thick layer of heatinsulating batch material and energizing the enveloped molten glassthrough electrodes, whereby the whole volume of molten glass becomes aninternal heat source at a temperature for progressively melting thecontiguous wrapping of batch material.

ln accordance with the present invention apparatus for meltingglassmaking batch material comprises a conveyor, a batch hopper abovethe conveyor and an associated pressure roller mounted above theconveyor to provide a pass to level the batch on the conveyor, a concaveroller below the conveyor to shape the conveyor for reception of thebatch, a second hopper for pouring molten glass centrally of the batchlayer, and a third hopper for the batch to cover the molten glass,perpendicular electrodes located to enter the molten glass through thecovering batch, and means for energizing the electrodes and convertingthe molten glass into a heat source surrounded by the batch material.

Such a method of melting glassmaking batch material will now bedescribed with reference to FIGS. 13 and 14 of the accompanyingdiagrammatic drawing.

In this arrangement a deformable conveyor 71 formed for example ofcanvas has its upper run supported by sets of rollers 72 and siderollers 73. The disposition of rollers 72 and 73 causes the conveyor 71to assume a troughlike form in its upper run.

Each of the rollers 72 is mounted on a shaft 74 supported in bearings 75carried by the machine frame (not shown) and rollers 73 are mounted onshafts 76 supported by bearing blocks 77, also carried by the machineframe. The conveyor 71 is displaced at uniform speed by motor 78connected to the shafts 74 of rollers 72.

The upper run of the conveyor 71 passes beneath a first batch feedhopper 79, which continuously discharges batch 22 onto the conveyor 71,which then passes beneath a forming roller 80 which compresses the batch22 and forms a longitudinal central depression therein. The compressedmaterial then passes beneath a glass dispensing hopper 81 whichcontinuously releases molten glass 21 into the depression in thecompressed batch 22 made by roller 80, and then the molten glass passesbeneath a second batch dispensing hopper 82 which continuously dispensesbatch 22 onto the molten glass 21 to completely cover said glass 21 witha thick batch layer.

Thus, as will be seen from FIG. 13, the contents of the conveyor 71after charging, comprise an extended volume of batch 22 lying lengthwiseof the conveyor 71 with a molten glass core 21 passing through thecenter of the cross section of batch 22 and thus, as with the otherembodiments hereinbefore described, the batch 22 insulates the moltenglass 21, the glass 21 transmitting heat to the batch 22.

As the conveyor 71 passes from beneath hopper 82, electrode pairs 14, 16having flexible electrical connections 83, are inserted downwardlythrough the cover of batch material 22 into the molten glass 21. Theelectrodes l4, 16 are inserted at spaced intervals along the length ofthe conveyor 71 carrying batch 22 and glass 21 and thus heating currentcan be passed between selected pairs of electrodes 14, 16 and the moltenglass 21 to maintain the molten glass 21 at the desired meltingtemperature.

The electrodes l4, 16 are attached to carriages 84 which are traversedalong a rail 85 so that the electrodes 14, 16 are displaced with theconveyor 71.

The temperature of the molten glass 21 can therefore be maintained atthe desired level by suitable regulation of the heating current and, asthere is a very high temperature difference between the molten glass 21and the enveloping batch 22, heat is transmitted to the internal surfaceof the batch 22 defining a core area and the heat insulating propertiesof the batch 22 resist the transmission of heat to the external limitsof the elongated body of batch 22 lying on the conveyor 71 until theheating operation is well advanced.

At the discharge end of conveyor 71 the electrodes 14, 16 are removedand as the conveyor 71 passes over its end supporting roller 86, themixed batch 22 and glass 21 is allowed to fall from the conveyor 71 ontoan apron P and thus into the glass tank, generally indicated byreference letter G.

By carefully relating the volumes of the batch 22 and molten glass 21delivered to the conveyor 71 and controlling the heat imparted to theglass 21 by the electric heating current the total amount of heatimparted to the batch 22 leaving the conveyor 71 for delivery to theglass tank G can constitute a very high percentage of the total heatinput required to convert the batch 22 to glass. Further, as the batch22 insulates the conveyor 71 from the heat source, conventional beltmaterials other than canvas can be used for the construction of theconveyor 71.

lclaim:

1. A method of feeding glassmaking batch material to a glass meltingtank, comprising the steps of forming a coherent body of the batchmaterial, providing a heat'source in a core area of the coherent body,the core area of said body being transformed into molten glass by theheat source and being progressively enlarged as melting takes place, theouter mass of unmolten material acting to converse the heat appliedinternally thereof, and feeding the preheated and partially molten bodyof batch material into a glass melting tank.

2. A method according to claim 1, wherein the heat source includesmolten glass.

3. A method according to claim 1, wherein the coherent body is encasedin a retaining wall to maintain sufficient structural strength in thebody when the internal batch surface defining the core area hasretreated to the outer regions of the coherent body.

4. A method according to claim 3, wherein the retaining wall is formedby fritting the outer region of the coherent body.

5. A method according to claim 3, wherein the said retaining wall isformed of glass compatible with the molten glass developed from thebatch material.

6. A method according to claim 1, wherein the coherent body is in layerform and the layer contiguous to and surrounding the core area comprisesone or more of the batch components having the highest melting point,the succeeding surrounding layers comprising components of progressivelylower melting points.

7. A method according to claim 2, wherein the core area is charged withcompatible cullet which is melted to expedite the provision of a heatsource in the form of an electrically conducting body of molten glass inthe core area.

8. A method according to claim 2, wherein the core area is provided witha coiled compatible glass with which coiled compatible glass there isoperatively associated an electrical conductor through which current ispassed to expedite the provision of an electrically conductive heatsource of molten glass in the core area of the coherent body of batchmaterial.

9. A method according to claim 1, wherein the coherent body is encasedin a retaining wall coaxial with the core area, and a concentric tubulargas vent is constituted above the heat source by a filling of looselypacked batch material extending from within the core area through anopening in the retaining wall.

10. A method according to claim 1, wherein the body of batch material isportable and has a vacant core area constituted by a central socket ofsmall volume as compared with the volume of the coherent body, saidsocket being effective to receive a heat source for continuallytransmitting heat to the coherent body.

11. A method according to claim 1 of feeding glassmaking batch materialto a glass melting tank having a doghouse, comprising forming the batchmaterial into a tubular body, locating the tubular body in the doghouseof the glass melting tank in coaxial alignment with a set of burnersmounted in ports in opposed walls of the doghouse, the burnersprojecting a flame at batch melting temperature into each endalternately of the tubular body to transform the inner surface of thetubular body into said heat source and the outer surface of the tubularbody being simultaneously fritted by the ambient heat in the doghouse,and then rolling the preheated and partially molten body of batch intothe glass melting tank.

12. A method according to claim 1, wherein the heat source in the corearea of the batch material is formed by spreading a layer of coherentbatch material on a deformable support, forming in the layer a channelextending longitudinally of the layer and pouring molten glass into thechannel, covering the molten glass with a layer of batch material,projecting aligned electrodes in spaced relation into the molten glassand energizing the electrodes to heat the batch material.

13. A method of feeding glassmaking batch material to a glass meltingtank furnace, comprising making a rollable hollow body of the batch, thebody having a bore, applying heat to the batch through the bore of thehollow body to progressively melt the material defining the bore,maintaining the internal heat treatment so long as the wall thickness ofthe body is sufficient to ensure rollability, advancing the internallymelted body to the feeding end of the tank and allowing it to dwell inthe feeding end thereby subjecting the external surface of the hollowbody to the heating effect of the furnace gases, and thereafter rollingthe preheated and partially molten body of batch into the glass meltingtank.

14. Apparatus for feeding glassmaking batch material to a glass meltingtank, comprising means for internally preheating the core area of acoherent body of glassmaking batch material thereby to transform batchmaterial in said core area into molten glass, said preheating meansbeing disposed upstream of the glass melting tank, and means for feedingthe preheated and partially molten body of batch material into the glassmelting tank.

15. Apparatus according to claim 14, wherein the glass melting tank hasa doghouse with ports in opposite sidewalls thereof, the body of batchmaterial is a tubular body, and the preheating means comprise a set ofburners mounted in said ports in coaxial alignment with the tubular bodyof batch material, the burners being arranged to project a flame intoeach end alternately of the tubular body.

16. Apparatus according to claim 15, wherein the body of batch materialis a rollable hollow body, and means are pro vided for rolling the bodythrough the doghouse into the glass melting tank.

17. Apparatus according to claim 14, wherein said feeding means comprisea pusher.

18. Apparatus according to claim 14, wherein the coherent body of batchmaterial is supported by a confining wall constituted by a fritted outerlayer of the body.

19. Apparatus according to claim 14, wherein the coherent body of batchmaterial has a bore and is supported within a container comprising abase, a tubular wall of glass, compatible with the batch material,rested on the base and a lid cooperating with the top of the wall, thelid being apertured coaxially with the tubular wall, a socket of glasscompatible with the batch material, and coaxial with the lid aperture,depending into the container at least to the core area of the body andsaid preheating means being coaxially mounted within said socket andgenerating in the core area of the body a glass melting temperature.

20. Apparatus according to claim 19, wherein the preheating meansinclude electrode means within the socket which generate heat to meltthe glass of the socket and thereby provide an electrically conductingbody of molten glass within the core area of the coherent body of batchmaterial.

21. Apparatus according to claim 20, wherein said electrode meanscomprise an electrode supported by said lid in coaxial relation with thesocket and extending into the socket and a matching electrode supportedby the base also extending into the socket, the operative ends of theelectrodes being axially spaced in the socket, and the base furthercarrying a connector for connecting the said matching electrode to amains terminal.

22. Apparatus according to claim 20, wherein said electrode meanscomprise a pair of parallel electrodes located in the central apertureof the lid and depending into the socket, said electrodes havinginwardly turned spaced feet within the socket.

23. Apparatus for feeding glassmaking batch material to a glass meltingtank, comprising in combination a conveyor. a batch hopper above theconveyor, and an associated pressure roller mounted above the conveyorto provide a pass to level the batch on the conveyor, a concave rollersupport below the conveyor to shape the conveyor for reception of thebatch, a second hopper for pouring molten glass centrally of the batchlayer, and a third hopper for discharging batch material to cover themolten glass, at least one pair of electrodes located to enter themolten glass through the covering batch, and

. means energizing the electrodes to convert the molten glass into aheat source surrounded by the batch material.

2. A method according to claim 1, wherein the heat source includes molten glass.
 3. A method according to claim 1, wherein the coherent body is encased in a retaining wall to maintain sufficient structural strength in the body when the internal batch surface defining the core area has retreaTed to the outer regions of the coherent body.
 4. A method according to claim 3, wherein the retaining wall is formed by fritting the outer region of the coherent body.
 5. A method according to claim 3, wherein the said retaining wall is formed of glass compatible with the molten glass developed from the batch material.
 6. A method according to claim 1, wherein the coherent body is in layer form and the layer contiguous to and surrounding the core area comprises one or more of the batch components having the highest melting point, the succeeding surrounding layers comprising components of progressively lower melting points.
 7. A method according to claim 2, wherein the core area is charged with compatible cullet which is melted to expedite the provision of a heat source in the form of an electrically conducting body of molten glass in the core area.
 8. A method according to claim 2, wherein the core area is provided with a coiled compatible glass with which coiled compatible glass there is operatively associated an electrical conductor through which current is passed to expedite the provision of an electrically conductive heat source of molten glass in the core area of the coherent body of batch material.
 9. A method according to claim 1, wherein the coherent body is encased in a retaining wall coaxial with the core area, and a concentric tubular gas vent is constituted above the heat source by a filling of loosely packed batch material extending from within the core area through an opening in the retaining wall.
 10. A method according to claim 1, wherein the body of batch material is portable and has a vacant core area constituted by a central socket of small volume as compared with the volume of the coherent body, said socket being effective to receive a heat source for continually transmitting heat to the coherent body.
 11. A method according to claim 1 of feeding glassmaking batch material to a glass melting tank having a doghouse, comprising forming the batch material into a tubular body, locating the tubular body in the doghouse of the glass melting tank in coaxial alignment with a set of burners mounted in ports in opposed walls of the doghouse, the burners projecting a flame at batch melting temperature into each end alternately of the tubular body to transform the inner surface of the tubular body into said heat source and the outer surface of the tubular body being simultaneously fritted by the ambient heat in the doghouse, and then rolling the preheated and partially molten body of batch into the glass melting tank.
 12. A method according to claim 1, wherein the heat source in the core area of the batch material is formed by spreading a layer of coherent batch material on a deformable support, forming in the layer a channel extending longitudinally of the layer and pouring molten glass into the channel, covering the molten glass with a layer of batch material, projecting aligned electrodes in spaced relation into the molten glass and energizing the electrodes to heat the batch material.
 13. A method of feeding glassmaking batch material to a glass melting tank furnace, comprising making a rollable hollow body of the batch, the body having a bore, applying heat to the batch through the bore of the hollow body to progressively melt the material defining the bore, maintaining the internal heat treatment so long as the wall thickness of the body is sufficient to ensure rollability, advancing the internally melted body to the feeding end of the tank and allowing it to dwell in the feeding end thereby subjecting the external surface of the hollow body to the heating effect of the furnace gases, and thereafter rolling the preheated and partially molten body of batch into the glass melting tank.
 14. Apparatus for feeding glassmaking batch material to a glass melting tank, comprising means for internally preheating the core area of a coherent body of glassmaking batch material thereby to transform batch material in said core area intO molten glass, said preheating means being disposed upstream of the glass melting tank, and means for feeding the preheated and partially molten body of batch material into the glass melting tank.
 15. Apparatus according to claim 14, wherein the glass melting tank has a doghouse with ports in opposite sidewalls thereof, the body of batch material is a tubular body, and the preheating means comprise a set of burners mounted in said ports in coaxial alignment with the tubular body of batch material, the burners being arranged to project a flame into each end alternately of the tubular body.
 16. Apparatus according to claim 15, wherein the body of batch material is a rollable hollow body, and means are provided for rolling the body through the doghouse into the glass melting tank.
 17. Apparatus according to claim 14, wherein said feeding means comprise a pusher.
 18. Apparatus according to claim 14, wherein the coherent body of batch material is supported by a confining wall constituted by a fritted outer layer of the body.
 19. Apparatus according to claim 14, wherein the coherent body of batch material has a bore and is supported within a container comprising a base, a tubular wall of glass, compatible with the batch material, rested on the base and a lid cooperating with the top of the wall, the lid being apertured coaxially with the tubular wall, a socket of glass compatible with the batch material, and coaxial with the lid aperture, depending into the container at least to the core area of the body and said preheating means being coaxially mounted within said socket and generating in the core area of the body a glass melting temperature.
 20. Apparatus according to claim 19, wherein the preheating means include electrode means within the socket which generate heat to melt the glass of the socket and thereby provide an electrically conducting body of molten glass within the core area of the coherent body of batch material.
 21. Apparatus according to claim 20, wherein said electrode means comprise an electrode supported by said lid in coaxial relation with the socket and extending into the socket and a matching electrode supported by the base also extending into the socket, the operative ends of the electrodes being axially spaced in the socket, and the base further carrying a connector for connecting the said matching electrode to a mains terminal.
 22. Apparatus according to claim 20, wherein said electrode means comprise a pair of parallel electrodes located in the central aperture of the lid and depending into the socket, said electrodes having inwardly turned spaced feet within the socket.
 23. Apparatus for feeding glassmaking batch material to a glass melting tank, comprising in combination a conveyor, a batch hopper above the conveyor, and an associated pressure roller mounted above the conveyor to provide a pass to level the batch on the conveyor, a concave roller support below the conveyor to shape the conveyor for reception of the batch, a second hopper for pouring molten glass centrally of the batch layer, and a third hopper for discharging batch material to cover the molten glass, at least one pair of electrodes located to enter the molten glass through the covering batch, and means energizing the electrodes to convert the molten glass into a heat source surrounded by the batch material. 